PMID- 17037850
OWN - NLM
STAT- MEDLINE
DCOM- 20061208
LR  - 20190715
IS  - 1533-4880 (Print)
IS  - 1533-4880 (Linking)
VI  - 6
IP  - 8
DP  - 2006 Aug
TI  - The influence of urea on the structure of proteins in reversed micelles.
PG  - 2416-24
AB  - Static fluorescence measurements from the protein Tryptophan (Trp) residues and 
      circular dichroism (CD) spectroscopy were used to investigate changes on the 
      tertiary and secondary structures of the protein bovine serum albumin (BSA) and 
      the dimeric enzyme hexokinase (HK) type PII from yeast, entrapped in reversed 
      micelles (RMs). The latter were obtained from the amphiphilic AOT (sodium 
      bis-2-ethylhexyl sulfosuccinate) in n-hexane, at several water to surfactant 
      ratios, W. BSA and HK were found to be anchored at the RM interface in close 
      contact with the surfactant layer, regardless of the size of the waterpool. For 
      BSA, such interaction promotes partial protein unfolding, according to CD data 
      that showed a decrease in the content of helical structure from 66% in a buffer 
      solution to 48% in the micellar moiety. When urea was present in the micelle, 
      further loss in helical structure occurred, thus indicating that the combined 
      effect (micellar environment and urea) altered the BSA conformation to a greater 
      extent than did RM or urea alone. Interestingly, Trps probed the same environment 
      in the micelle, regardless of the presence of urea, but the fluorescence was 
      quenched to a higher extent with urea. Thus, the fluorofore emission must have 
      been affected either by the direct interaction of urea or by indirect exchange of 
      water structure caused by urea interacting with water and the micellar interface. 
      Both mechanisms might be of relevance in the solvation properties nearby the 
      Trps. For HK, an association between the enzyme and the micelle interface was 
      indicated in the CD spectra, which exhibited a randomized structure upon 
      interaction, whatever the RM droplet size. The urea addition to the micelle water 
      pool did not cause further impact on the HK conformation. In addition, the 
      influence of urea at the RM interface was not sensed by the exposed tryptophans 
      of the enzyme, unlike the results for BSA.
FAU - Caetano, Wilker
AU  - Caetano W
AD  - Instituto de Fisica, Depto. de Fisica Aplicada, Universidade de Sao Paulo, USP, 
      CP 66318, 05315-970 Sao Paulo/SP, Brazil.
FAU - Amaral, Carmem Lucia C
AU  - Amaral CL
FAU - Itri, Rosangela
AU  - Itri R
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
PL  - United States
TA  - J Nanosci Nanotechnol
JT  - Journal of nanoscience and nanotechnology
JID - 101088195
RN  - 0 (Micelles)
RN  - 0 (Proteins)
RN  - 0 (Surface-Active Agents)
RN  - 8W8T17847W (Urea)
RN  - EC 2.7.1.1 (Hexokinase)
SB  - IM
MH  - Animals
MH  - Cattle
MH  - Circular Dichroism
MH  - Hexokinase/chemistry
MH  - *Micelles
MH  - Nanotechnology/*methods
MH  - Protein Conformation
MH  - Protein Denaturation
MH  - Protein Structure, Secondary
MH  - Protein Structure, Tertiary
MH  - Proteins/*chemistry
MH  - Spectrometry, Fluorescence
MH  - Surface-Active Agents/chemistry
MH  - Urea/chemistry/*pharmacology
EDAT- 2006/10/14 09:00
MHDA- 2006/12/12 09:00
CRDT- 2006/10/14 09:00
PHST- 2006/10/14 09:00 [pubmed]
PHST- 2006/12/12 09:00 [medline]
PHST- 2006/10/14 09:00 [entrez]
AID - 10.1166/jnn.2006.518 [doi]
PST - ppublish
SO  - J Nanosci Nanotechnol. 2006 Aug;6(8):2416-24. doi: 10.1166/jnn.2006.518.